Redid all shop images.

Reworked all shop images to always be 2x2 pixel blocks (2/3rds the
original size), never scaled unevenly.

Also went through and touched up every image if needed, removing
transparent pixels for the hand on each weapon, removing arm outlines
from armors that don't cover the arm, and so on.

Also reorganized the shop files - in gear, each directory has its own shop subdirectory (as events/spring already did). The few remaining images were moved from gear/shop to shop.

Screenshots of the new version:
![new healer](https://f.cloud.github.com/assets/3161425/2496306/924a7876-b319-11e3-92cc-3af2a082e602.png)
![new rogue](https://f.cloud.github.com/assets/3161425/2496381/afc518b4-b31b-11e3-92fa-102a60de785b.png)
![new special](https://f.cloud.github.com/assets/3161425/2496383/b21cc616-b31b-11e3-9b48-809ebe8e453e.png)
![new warrior](https://f.cloud.github.com/assets/3161425/2496384/b434d542-b31b-11e3-842e-38d41e24b266.png)

And here's the current version:
![old healer](https://f.cloud.github.com/assets/3161425/2496385/bd081d14-b31b-11e3-8841-94b238ee262b.png)
![old rogue](https://f.cloud.github.com/assets/3161425/2496386/c2b36ed0-b31b-11e3-8379-d6a3e73946a6.png)
![old special](https://f.cloud.github.com/assets/3161425/2496387/c58323e4-b31b-11e3-9209-078b7da51512.png)
![old warrior](https://f.cloud.github.com/assets/3161425/2496389/c7a49360-b31b-11e3-8e44-8f61e6b37c6a.png)